(1) Field of the Invention.
This invention generally relates to coupling devices for use by electrical and plumbing contractors laying underground pipe or conduit. More particularly, this invention relates to machines facilitating the manual coupling of a pair of pipes aligned end to end.
(2) Description of Related Art Including Information Disclosed 37 CFR 1.97 and 1.98
Piping used by electrical or plumbing contractors usually have an annular collar at one end of each pipe, flaring slightly to form a slightly bell-shaped end. The other end of each pipe may be received telescopically in the bell-end collar of an adjacent aligned pipe when a pipeline is being formed.
In the assembly of such a pipeline, it often becomes necessary for each pipe to be pulled in the direction of the aligned collar until its end extends into the bell-end collar. Often considerable force may be required to draw them together, sometimes more force than workers can readily exert directly on the pipes; this may be especially true when the pipes are lying at the bottom of a trench, which is often the case. Therefore, various devices have been devised in the prior art to provide the necessary mechanical advantage to enable the workers to draw the pipes together. It is necessary that such devices apply little, if any, lateral force to the pipes as they are drawn together in order to maintain the pipes in alignment. Moreover, many modern pipelines are constructed of piping made of polyvinyl chloride (PVC) or similar plastic materials, that may buckle or bend upon application of force against the sides. Installing PVC pipe is labor intensive, and sometimes installers do not seat the pipe in the bell completely. When pipe is not seated completely, the pipe sometimes comes apart when covered up with dirt.
As mentioned above, it is the usual practice to assemble the pipe at the bottom of a trench. The width of the trench is made as narrow as possible to reduce costs. Thus the device used to assemble the pipes should be compact in size, in order to accommodate this minimum trench width.
It will be appreciated by those skilled in the art that one longstanding difficulty associated with layering bell-coupled pipe systems is the difficulty in carrying out the repetitive task of pulling adjacent pipe sections together, especially since there may be considerable frictional engagement between the male end within the bell-end. In the past, considerable difficulty has been experienced in properly holding a pair of plastic pipes in confronting and abutting relationship while the members were joined end to end or when pipes were disassembled. This is especially true when the two pipes had to be accurately joined together or when the pipe had to be disassembled in underground narrow trenches. Such difficulty was greatly increased where the plastic pipes were curved. For example, some plastic pipes are packaged in coils which may result in the pipes having an arc which creates difficulties in keeping the pipes straight when joining them.
Devices to facilitate coupling of piping have been available for several years. Known in the art are the following, arguably related to the patentability of the present invention.
U.S. Pat. No.1st InventorDate of Patent/Publication3,257,714DukeJun. 28, 19663,364,555SwinkJan. 23, 19683,435,507PronovostApr. 1, 19693,571,896WilkersonMar. 23, 19713,653,115PerkinsApr. 4, 19723,668,766CarterJun. 13, 19724,015,323TopperApr. 5, 19774,178,668GeorgeDec. 18, 19794,519,122MillerMay 28, 19854,598,452IsekiJul. 8, 19864,748,730GeorgeJun. 7, 19884,893,393MarshallJan. 16, 1990
There are several patents that disclose a pair of clamps for gripping the two pipes, and a handle actuated leverage assembly. For example, see U.S. Pat. No. 4,519,122 issued to Miller, U.S. Pat. No. 3,653,115 issued to Perkins and U.S. Pat. No. 4,598,452 issued to Iseki. However, none of those patents discloses a guide track channel on the leverage assembly, terminating with a drop notch enabling additional leveraging/coupling.
U.S. Pat. No. 4,748,730 issued to George discloses a pair of semi-circular pipe straddling assemblies (linked by a pair of rods), one assembly straddling a pipe near its bell end and the other straddling a free section of pipe near its spigot end. One of the straddling assemblies includes a pair of cam disks having marginal teeth, both toothed cams pivotally operable against opposite sides of the free section of pipe captured between that straddling assembly; repetitive movement of an actuator handle, reciprocatingly back and forth along the direction of the aligned pipes, causes the toothed cams to alternately extend inwardly through spacing in the respective straddling assembly, to engage and pull the pipe (and then withdraw out of engagement with the pipe), thereby ratcheting the spigot end of the free pipe section into frictional seating within the bell end of the other pipe. This patent does not disclose a pair of clamp grips. Moreover, this patent does not disclose a guide track channel on the leverage assembly, terminating with a drop notch enabling additional leveraging/coupling.